LUMINESCENCE AND FLUORESCENCE LINE NARROWING STUDIES OF Y3AL5O12-MN4+

A luminescence study of the Y₃Al₅O₁₂:Mn⁴⁺ system is presented. Luminescence is due to ²E → ⁴A₂ transitions on Mn⁴⁺ ions which substitute for Al³⁺ ions in distorted octahedral sites. The technique of fluorescence line narrowing (FLN) is used to interrogate some of the details of this transition. The zero-phonon R lines are found to be a composite of transitions from Mn⁴⁺ ions in different sites, the strongest line coming from Mn⁴⁺ ions in regular Al³⁺ sites. The ratio of R line to sideband in the emission from Mn⁴⁺ ions in these regular sites is found to be unusually low, and this is taken as an indication of an ion-lattice coupling for the Mn⁴⁺ ion which is significantly stronger than for the case of the Cr³⁺ ion in Y₃Al₅O₁₂. Measurements of the luminescence decay rates as a function of temperature are given and we attempt to relate these data to models for nonradiative processes.